Montgomery County’s controversial bag tax took in double the anticipated revenue in its first year and County Executive Isiah Leggett suspects out-of-county shoppers have something to do with it.

County data shows the tax generated about $2 million through the end of November 2012 from taxing shoppers 5 cents for each carryout bag.

County spokesman Patrick Lacefield said county estimates on final year-end figures that were not yet available will show about $2.2 million total revenue from the bag tax in calendar year 2012, about double the $1.2 million Leggett projected it would generate in its first year.

The number of retailers reporting continued to increase with each reporting period in 2012, as more retailers reached the $100 threshold for filing required tax reports and remitting payments, Lacefield said in an email.

Using his personal shopping experience as a guide, Leggett said he believes shoppers from out of the county are driving the higher revenue.

“A good part of that revenue comes as a result of people shopping here who are tourists, who are not accustomed to the law or are from a neighboring jurisdiction that does not have the tax,” Leggett said.

But to put numbers behind his theory, and understand exactly what drove the revenue higher than anticipated, the executive said his staff will have to further analyze its data on the tax.

Justified as a means to mitigating pollution from carryout bags, the tax went into effect in January 2012. The revenue goes to the county’s Water Quality Protection Charge Fund.

Last year, Leggett said repeatedly that the county does not view the tax as a revenue stream for the Water Quality Protection Charge Fund, but rather a program to curtail waste and encourage the use of reusable bags.

Anecdotally, he said, it is working to reduce waste.

“We do see some improvements on streets and in streams,” he said. Leggett said he also sees shoppers toting their own reusable bags into stores.

But, again, more data and more analysis are needed for the county to quantify the impact the tax has had on the environment and on shoppers and retailers, he said.

Council President Nancy Navarro (D-Dist. 4) of Silver Spring said she has heard from some constituents about the difficulty of adjusting to bringing their own bags to malls and restaurants.

“But there seems to be more of an acceptance for the grocery store,” she said.

While a review of the tax is not on the council’s agenda currently, Navarro said she plans to raise it with her colleagues to see if it will be revisited.

Leggett said he looks to have Montgomery’s CountyStat efficiency program study the tax as well.